A particulate filter (PF) may be used to reduce particulate matter emissions in engines, such as diesel engines. The PF may be periodically regenerated to remove accumulated particulate matter. The regeneration may be achieved by raising the temperature of the PF to a predetermined level to oxidize the accumulated particulate matter.
Timing of the PF regeneration may affect the operational life of the PF since regeneration of a PF overloaded with particulate matter may generate overly high temperatures and potentially degrade the PF ceramics due to overheating. On the other hand, too frequent regeneration may result in reduced fuel economy, as energy is used to raise the exhaust temperature. Further, too frequent regeneration may result dilution of engine lubricating oil, thereby causing increased warranty due to higher component wear.
Timing of the regeneration of PF particulate matter may be provided based on estimates of soot load, or based on differential pressure measurements across the filter, for example, along with monitoring of other parameters such as temperature.
The inventors herein have recognized various issues with such approaches. In particular, pressure-based measurements may be too inaccurate at low exhaust volume flows due to degraded accuracy of sensors at the limits of their operating range. In addition, pressure-based measurements may be too inaccurate during transient conditions due to high time constants of the sensors and unsteady fluid dynamics in the exhaust system.
To at least partially address the above mentioned issues, the inventors herein provide various systems and methods for updating the PF soot load of an engine. In one embodiment, the method may include performing regeneration in response to both pressure-based measurements as well as estimated soot loading independent of the pressure-based measurements, where during conditions in which the pressure-based measurements may be inaccurate, the soot load is estimated based on operating conditions and previous pressure-based measurements that occurred during previous conditions in which the pressure-based measurements are more accurate. In this way, more continuous monitoring of particulate filter loading is provided, while taking advantage of pressure-based measurements from the most recent accurate reading, for example, and operating conditions that have transpired since such reading, including transient conditions. Thus, more appropriately timed regeneration may be provided.